I actually made this by adapting my Crystal Shell weakaura...
All you need to do is change all the instances of UnitBuff to UnitDebuff and take into account that it caps out at 75% of your max hp (not 100% like blood shield).
If you want to see where it came from:

I love the weak aura from your last post on the 22nd but for some reason it is now generating a ton of lua errors. I am definitely not good at coding so I haven't been able to resolve it. Was wondering if you guys were still using it and if so are you having issues with it generating errors for you?

Last edited by Crossfire72; 2013-11-08 at 08:06 PM.
Reason: mispelling